Technical Field
This disclosure relates to ripple monitoring systems and methods that may be embedded in an integrated circuit (“IC”). The ripple monitoring may be used to monitor power supply operations.
Description of Related Art
Power supplies of high performance microprocessors or high density ASICs or FPGAs, commonly referred to as “switching power supplies,” may have demanding specifications for line and load regulation, load transient response, and/or residual ripple voltage caused by their inherent switching operation.
Electrical components in such power supplies may degrade which, in turn, may impair the ability of the power supplies to meet one or more specifications. Ageing electrolytic capacitors, for example, can be particularly problematic. Due to electrolyte evaporation or other aging processes over their operational lifetime, their equivalent series resistance (ESR) may increase and their capacitance may decrease. This may cause the affected power supply to operate unreliably.
Operating from an out-of-spec power supply may cause random failures, such as occasional memory loss, false calculations, tripping of watchdog timers, and/or a need to reset and/or reboot the entire system from time to time. Such failures may occur rarely at first, and only under specific temperature, line or load conditions. They may be hard or almost impossible to catch by common power supply supervisor ICs, as their trip points may be set to detect out-of-spec power supply voltages. But by then, it may be too late, especially for high reliability and/or high availability systems.
Fast comparators can be found in some IC products, known as “Power Supply Managers,” such as the LTC2978 of Linear Technology Corporation (“LTC”). These may be user programmed to stringent trip points. However, this approach to detect degrading power supplies before the system fails can be a tightrope walk at best, between false alarms happening too often, and not being able to detect an unfolding problem soon enough. This may be due to the mixed nature of the power supply ripple, which may have ripple components caused by switching power supply operation and by varying or periodic load currents and/or load current transients, and the two state nature of any comparator output signal not being able to convey much supporting information.